In general, when a trolling motor is stalled due to prop entanglement or other prop disruptions that slow or stop shaft rotation, then motor surge-currents, excess sustained currents, and over-heating of all main current components can cause partial to total failure of various system components and put the trolling motor at risk for unwanted operations and/or the possibility of fire.
When corrective means are applied to an intermittent stalled motor over-current condition, then a secondary response time problem is presented. If the corrective system is too fast then intermittent stalls will create an undesirable intermittent operation, but if the corrective system is too slow then locked rotor stalls can quickly overcome the system with damage.
Existing motor protection methods either regulate the current to a maximum value or shuts off the entire system like a circuit breaker which requires a total power up sequence. Methods that regulate stall current to a safe level for the electronics is still not safe for the user since the motor will immediately start turning when the user frees the obstruction from the prop that has the motor in the stall condition. When the prop starts turning immediately then the user is at risk for injury. The method that shuts everything off and requires power-up is safe but a very unnecessary nuisance.
The existing motor protection solutions are typically fixed at detecting stalled conditions at 100% voltage, similar to a circuit breaker configuration, wherein a stalled condition that occurs at 50% voltage or 75% voltage or any other percentage of voltage would not be detected properly. As an example, if a motor is operating at 50% of the pulse width modulation (PWM) signal voltage and the motor of the trolling motor is wound up in a weed or other obstruction, a user is only protected if the motor is operating at 100% PWM. In the case of this example, a user may raise the motor up, remove the weeds from the motor, and because the motor was only operating at 50% PWM, there is a good chance that the motor starts up while the user is removing the weeds from the motor, as the obstruction in this case would not trip a circuit fixed at 100% PWM. What is needed then is a proportional reference, and not a fixed reference in such a circuit.